Detail of "12178-37-9"

Reference

Weathering products of the Upper Triassic of Middle Dalmatia [Southern Croatia]

Weathering products of the Upper Triassic of Middle Dalmatia [Southern Croatia]. Sinkovec, Boris; Susnjara, Ante; Sakac, Kresimir (Dep. Mineral., Pet. Econ. Geol., Fac. Min., Geol. Pet. Eng., Zabreb, Yugoslavia). Geol. Vjesn., 28, 311-19 (Croatian) 1975. CODEN: GEVJAO. DOCUMENT TYPE: Journal CA Section: 53 (Mineralogical and Geological Chemistry) Occurrences of bauxite [1318-16-7] and other weathering products lie near Knin and Trilj. The sediments near Trilj contain kaolinite, berthierine, illite, hematite, titanite, and tourmaline. Those near Knin contain kaolinite, boehmite, diaspore, illite, hematite, zircon, and goethite but some deposits near Jabuka contain Fe-chlorite and small amts. of titanite and secondary goethite. The structure of the examd. weathering products and their chem. and mineralogical compn. indicate minor differences in their origin. Kaolinite [1318-74-7] crystals formed in clayey muds with large sedimentational vols. The oxidizing conditions predominating in the beginning of Fe deposition as hematite [1317-60-8] or goethite [1310-14-1] changed to reducing conditions, so that berthierine [12178-37-9] formed from the remaining SiO2, Al2O3, and Fe2O3 gels (preliminarily reduced to Fe2+). In some cases, bauxites show traces of resedimentation accompanied by partial bauxitization of clays. The sediments at Jabuka contain quasi-exclusively Fe-chlorite crystd. from the muds in a reducing environment. The deposits were eroded after crystn. and round grains accumulated from Fe-chlorite resedimented under conditions similar to those in the primary sediments.

Iron and glauconites from the Congo River mouth

Iron and glauconites from the Congo River mouth. Giresse, Pierre (Cent. Rech. Sedimentol. Mar., Univ. Perpignan, Perpignan 66025, Fr.). Sci. Geol., Bull., 38(4), 293-322 (French) 1985. CODEN: BIGPA8. ISSN: 0302-2692. DOCUMENT TYPE: Journal CA Section: 53 (Mineralogical and Geological Chemistry) Section cross-reference(s): 3 Sedimentary and stratigraphic studies were made of the magnetic and size fractions of Late Quaternary continental shelf sediments offshore of the mouth of the Congo River. Several stages of authigenic mineral development in the Late Quaternary were identified. At ~18,000 yr ago, during the last marine regression, the concn. of fecal pellets on the outer shelf produced the oldest glauconite [1317-57-3] on the shelf. At ~12,000 yr ago, skeletal calcareous sediments accumulated; green grains (glauconite) are less abundant in these sediments and the dominant authigenic Fe mineral is a potassian nontronite [106311-86-8]. Three zones of authigenic Fe mineralization are distinguished in Holocene sediments: (1) green grains (glauconite) are the dominant authigenic Fe minerals far from areas of active sedimentation, (2) potassian nontronite is the dominant authigenic Fe mineral in zones of detrital sedimentation offshore of the river's mouth, and (3) bertheriene [12178-37-9] is the dominan authigenic Fe mineral in submerged, org. matter-rich sediments of the river delta.